The present invention is in the field of gas discharge devices and more particularly relates to gas plasma display devices.
Devices displaying electrically generated light phenomena are well known in the prior art. Early devices were developed along with the development of continuous sources of high potentials. Such high potentials permitted the generation of glow discharges in response to resultant electric currents in reduced pressure, air-filled vessels, with currents being on the order of microamperes up to tens of milliamperes at tens of thousands of volts. High voltage, high frequency effects were demonstrated by Nikoli Tesla in the early part of this century, based on the production of gas discharges in various gas filled vessels by induced currents generated by remote apparatus.
More recently, knowledge of the physics and chemistry of electrically generated gaseous discharges have led to the commercially significant development of devices like the neon sign and the flourescent lamp.
In addition, various plasma display devices have been developed based upon gas discharges. U.S. Pat. No. 2,004,577, U.S. Pat. No. 3,621,332, U.S. Pat. No. 3,629,654 and U.S. Pat. No. 4,035,690 illustrate such devices which are particularly useful in connection with alphanumeric displays often used in connection with digital computers and other instrumentation.
Further, plasma displays have also been developed into an art form. For example, transparent non-conductive spherical shells have been used to enclose regions containing ionizable gases, such as neon, and a hemispherical electrode. In such devices, external power supplies and associated circuitry coupled to the electrode establish a high frequency electric field within the spherical shell (or enclosure) between the enclosed electrode and an external ground electrode. Visible electric discharges form along the electric field within the shell. At the high frequencies of the excitations, the resultant electric fields may be maintained at sufficiently low amplitude to not penetrate human skin, or cause tissue damage, yet still establish a visible discharge within the shell. These dynamic and highly visual discharges can be observed to change in location and intensity by proximity with a conductive body such as a user's hand. The operation of such a device depends upon the conductive nature of an ionized gas within the shell to form the first element of a capacitor, the wall of a hollow glass enclosure as the dielectric for that capacitor and a conductive object, for example, a user's hand, as the second element. Changes in the location of the second element will affect the areas of highest capacitive coupling, perturbing the distribution of ionized gas in the shell, producing user controlled variable visible effects. The capacitive coupling to human tissue is due to the high concentration of water and various ions in the body. Such devices permit a user to directly and safely interact with the electric field and visual discharge inside the shell.
However, the geometry of such prior art devices generally permits the electric field within the shell to extend substantially omnidirectionally from the discharge electrode in the shell. Moreover, the power supply and excitation network were considerably spaced apart from the discharge region. As a consequence of these factors, the user could very well interact with the field at points closer to the discharge electrode than the effective ground electrode. Prior art displays have not existed where the power supply (and effective ground electrode) were positioned closer to the discharge electrode than an interactive conductive bodies could be positioned.
It is an object of the present invention to provide an improved gas display device.
Another object is to provide an improved gas display device with a self contained power supply and excitation network.